I've attached a PDF file that I created which includes most of the voice commands available in the 2008 CTS 40GB HDD system, including commands for guidance, maps, phones, and the music system.
The file is 2 pages. It should be printed on both sides of a single sheet of 8.5" X 11" paper, then folded into thirds to form a brochure-type document that you can keep in the car's armrest.
Because there are a great many commands for the music system, I've consolidated them to save space and to avoid using an even smaller font. It should be self explanatory, but note that "Music" is a command that controls the HDD or the AUX/USB.
Please let me know if you find errors or significant omissions, and I'll update the file.